Method for classification of year-related data fields in a program

ABSTRACT

The method of the invention enables a computer to examine a software application, which includes operands and operators, and to identify operand fields which include a year value. A scan knowledge base includes scan rules that enable characteristics of operands to recognized, identified and initially classified. An operand association table is provided for each operator and indicates, based upon inter-relationships of operands associated with the operator, whether an associated operand that has been initially classified as a year field or a probable year field, should be assigned a revised classification and what that revised classification should be. The method reviews the application, using the scan knowledge base, to identify each operand which can be initially classified as a year field or a probable year field and lists each such operand in an operand table. The method also reviews the application to identify every operator listed therein and lists every operator and any associated operands in an operator table. Thereafter, the method determines, for operator entries located in the operator table, and from operands associated therewith and an operand association table, whether the classification for each respective operand in the operand table should or should not be altered.

This application is a Continuation in Part of U.S. patent application, Ser. No. 08/705,499, filed Aug. 29, 1996 and entitled "Method for Classification of Year-Related Data Fields in a Program".

FIELD OF THE INVENTION

This invention relates to a method for avoiding calculation ambiguities which result from the use or year dates from the year 2000 and forward and, more particularly, to an improved method for finding year-related data fields in a program to enable their later alteration into an improved year format.

BACKGROUND OF THE INVENTION

Software applications use dates in many operations, from complex financial transactions to the calculation of expiration dates of drivers' licenses and credit cards. Many such applications base their calculations on dates and subtract two-digit year values to arrive at a calculation result. For example, calculations of interest on a 5-year certificate of deposit involve the subtraction of the certificate's issue date from the current date and a determination of interest based upon the difference value. This calculation is not a problem if the certificate matures in 1999, but if it matures in 2001, the same computation can result in an error message or worse. In the year 2000, the two-digit year indication starts over at "00" and unless something distinguishes such date, the year will appear to be the year 1900--or so it will seem to many programs that use only the year's last two digits for dates.

In the early days of data processing, storage space was at a premium and it was decided to use two digits for the year indication. Most programs today carry forward that format and employ two bytes of 8-bit binary data to indicate the last two-decimal values of the year. Many of these programs/applications were written years ago and the authors/programmers who understood their organization and details are no longer available for consultation. Further, calculations employing year fields are often deeply embedded in very large program routines and are thus difficult to find and identify.

The key to identifying year fields in a program, at a reasonable cost, is to do so automatically and avoid the use of programmers to scan the code.

Year fields are normally composites of sub-fields. That is, the fields used to represent "year", "month" and "day" are sub-fields of a larger field of "date". To identify such fields, two primary matching techniques are currently being used. The first examines the labels assigned to various data fields used by the program. In COBOL, these labels are found in the DataDivision which is the area of the program which defines each of the data elements used in the program. Using various techniques, key phrases like "year", "yr", etc. are located in the labels. These data fields are then considered to be year-oriented fields. As a further check, the format of each such "year-oriented" field is determined and is scanned to see if it meets one of the commonly used formats for year information. The most common format in use involves three two-digit numbers that are defined consecutively.

The application of this dual test allows a search of a program to be carried out and often leads to the discovery of approximately 80% of the year fields. Because such a search procedure does not consider the interrelationship of a discovered year field with other year fields, both in the same program and in allied programs in the same application, data that would allow a more accurate year field determination is ignored.

Accordingly, it is an object of this invention to provide an improved method for identifying year-related fields in a program.

It is another object of this invention to provide an improved method for identifying year-related fields in a program, which employs data available in associated fields to assure a higher level of accuracy in the year field identification process.

It is another object of this invention to utilize classifications other than purely year oriented fields; for example classifications such as day, month, currency, durations and (when separated from years) centuries may also be used to evaluate applications. Weighted classifications may be assigned to improve the year finding process.

SUMMARY OF THE INVENTION

The method of the invention enables a computer to examine a software application, which includes operands and operators, and to identify operand fields which include a year value. A scan knowledge base includes scan rules that enable characteristics of operands to recognized, identified and initially classified. An operand association table is provided for each operator and indicates, based upon inter-relationships of operands associated with the operator, whether an associated operand that has been initially classified as a year field or a probable year field, should be assigned a revised classification and what that revised classification should be. The method reviews the application, using the scan knowledge base, to identify each operand which can be initially classified as a year field or a probable year field and lists each such operand in an operand table. The method also reviews the application to identify every operator listed therein and lists every operator and any associated operands in an operator table. Thereafter, the method determines, for operator entries located in the operator table, and from operands associated therewith and an operand association table, whether the classification for each respective operand in the operand table should or should not be altered.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a computer system which is adapted to perform the method of the invention.

FIG. 2 is a schematic representation of an operand table employed with the method of the invention.

FIG. 3 is a schematic representation of an operator table employed with the method of the invention.

FIGS. 4a-4d illustrate a flow diagram of the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a computer system adapted to carry out the method of the invention. A central processing unit (CPU) 10 is coupled via a bus system 12 to a program memory 14 which includes an application 16 which, in turn, comprises plural component programs 18, 20, 22, etc. Program memory 14 further includes: a year field classification procedure 24; two tables, an operand table 26 and an operator table 28; and a scan knowledge base 29 with scan rules that enable characteristics of operands to be identified and classified. Year field classification procedure 24 is loaded into program memory 14 from disk drive 26, into which an appropriate magnetic disk entry device has been inserted. A further memory 28 provides storage for data files that are employed with application 16 and component programs 18, 20, 22 etc.

The usage of the term "year field" hereafter will refer to a field within application 16 (or any of its component programs) which holds or will hold a year value. A data field classified as a "year field" will be a field that is, with high probability, a field which contains a year indication. A data field classified as a "probable year field" refers to a field which may include a year designation, with some given level of probability. A data field classified as a non-year field refers to a field that currently has a very low probability of being a year field

Year field classification procedure 24 initially constructs a data base from all of the component programs in application 16 and employs an operand table (FIG. 2), an operator table (FIG. 3), and a plurality of operand association tables (Tables B-E below) to enable the performance of the year field classification procedure. Initially the application program code is parsed and each data definition label is placed into a first operand table. Each operator and associated operands from the parsed code are placed into an operator table. The operand table contains space that is used to indicate the classification of each operand and whether the classification of the operand has changed since the last time it was analyzed (e.g., a flag).

Initially, the application is scanned to identify year fields, probable year fields and non-year fields. The year fields are then used as a starting point for a complete analysis of the application to identify most, if not all, of the year fields used in the application.

Turning to FIGS. 2 and 3, the tables employed during the analysis of the application will be described. In FIG. 2, operand table 26 is schematically illustrated. Operand table 26 includes a listing 30 of each operand that is present in application 16. Assuming that application 16 is written in COBOL, the operands are derived from the data definitions section of the program. A format column 32 is associated with each operand and defines the format of the field. For instance, if the label includes an indicator "PIC 99", a type of display format is indicated; if the label includes the phrase "COMP", a binary word format is indicated, . . . etc . . . . A third column 34 of operand table 26 is occupied by a probability value which indicates whether the operand is classified as a year, a probable year, or a non-year. A fourth column 35 indicates if any reclassification has occurred.

As will hereafter be understood, each operand is initially classified as to its year "type" through use of one or more prior art analysis techniques. Thereafter, each operand that is classified as a year is subjected to further tests, in accord with the invention hereof, which enables a refinement of the classification, and a resulting more accurate classification indication.

Operator table 28 (FIG. 3) is utilized by the method of the invention and lists in column 36 every operator found in application 16. Along with each operator, is listed one or more associated operands (i.e., operands I-III in columns 38, 40 and 42, respectively), along with a current classification of each of the aforesaid operands in columns 44, 46 and 48.

An operand may be assigned a different, non-unique classification for each operand instance in the operator table, since an operand may represent both a year and a non-year at varying points in the program. Such an operand is hereafter called a "resolvable modal". A resolvable modal is illustrated by the following pseudo code:

    ______________________________________                                         line 100     HIRE-DATE = TODAYS-DATE.                                          line 101     HIRE-DATE = EMPLOYEE-NAME.                                        ______________________________________                                    

EXAMPLE A

In the pseudo code of Example A, there are three operands: HIRE-DATE, TODAYS-DATE and EMPLOYEE-NAME, and three operand instances: two HIRE-DATE instances, one TODAYS-DATE instance and one EMPLOYEE-NAME instance. For this example, assume TODAYS-DATE is really a date and has been previously classified as such. Moreover assume that and that EMPLOYEE-NAME is really the name of an employee and has been previously classified as such.

The first operand instance of HIRE-DATE, on line 100, is associated with a date. The second operand instance of HIRE-DATE, on line 101 is associated with a name. The HIRE-DATE operand is classified as a resolvable modal since the two operand instances of HIRE-DATE can be classified independently, or in other words, resolved by operand instance. In Example A, the first operand instance of HIRE-DATE, on line 100, would be classified as a date and the second operand instance, on line 101, of HIRE-DATE would be classified as a name.

If, for a given operand instance, the classifications result in two incompatible classifications (e.g. a year and not year) based on conditional code flow, the operand instance is referred to as an "unresolvable modal". An unresolvable modal is illustrated by the following pseudo code:

    ______________________________________                                         line 200   IF HIRE-DATE = TODAYS-DATE THEN                                     line 201     HIRE-DATE = TOMORROWS-DATE                                        line 202   ELSE                                                                line 203     HIRE-DATE = EMPLOYEE-NAME.                                        line 204   PRINT HIRE-DATE.                                                    ______________________________________                                    

EXAMPLE B

In the pseudo code of Example B, there are four operands: HIRE-DATE, TODAYS-DATE, TOMORROWS-DATE and EMPLOYEE-NAME. There are seven operand instances: four HIRE-DATE instances and one operand instance for each of the other operands TODAYS-DATE, TOMORROWS-DATE and EMPLOYEE-NAME. For this example, assume TODAYS-DATE and TOMORROWS-DATE are really dates and have been previously classified as such. Moreover assume that EMPLOYEE-NAME is really the name of an employee and has been previously classified as such.

The first operand instance of HIRE-DATE, on line 200, cannot be classified, as yet. The second operand instance of HIRE-DATE, on line 201, is associated with a date. The third operand instance of HIRE-DATE, on line 203, is associated with a name. The fourth operand instance of HIRE-DATE is printed out. In Example B, it will be determined that the fourth operand instance HIRE-DATE, on line 204, is the unresolvable modal. Since the IF statement may be true and not true, it is impossible to determine if the fourth operand instance of HIRE-DATE, on line 204, is a date or a name. If the condition HIRE-DATE=TODAYS-DATE is true, line 201 is applied and the fourth operand instance is a date. If the condition HIRE-DATE=TODAYS-DATE is false, line 203 is applied and the fourth operand instance is a name. The fourth operand instance thus cannot be resolved, since the operand instances may fall into one of two classifications. The forth operand instance is then classified as an unresolvable modal.

Operator table 28 (FIG. 3) supports the ability to assign a different classification for each operand instance in the operator table by assigning the appropriate classification to the operand using one or more of the columns 44, 46 or 48. In the case where an operand instance is modal (resolvable or unresolvable) the operand is classified as modal in the operand table (FIG. 2), since the operator table (FIG. 3) would have to assign at least two different classifications for the operand instances (e.g. Year and Not Year).

In the case that an operand instance is an unresolvable modal, the classification is assigned an unresolvable modal classification for the operand in the operand table (FIG. 2). The operand instance which is an unresolvable modal results in an unresolvable modal classification being inserted into operator table columns 44, 46 or 48 depending upon which operand is the unresolvable modal.

Operand column 30 and format column 32 in operand table 26 and operator and operand columns 36, 38, 40 and 42 in operator table 28 are built during the initial parsing operation of application 16. Thereafter, any of a plurality of known search procedures can be employed to assign an initial year classification to each operand in operand table 26. For instance, the characteristics that can be used to establish the initial classification of a year field are:

1. An operand label which indicates a year. For instance, key phrases like "year", "Yr", located in the label provide such an indication.

2. The operand label is constructed in a data format that is compatible with a year indication. For instance, the following COBOL code fragment appearing in the data division is indicative of the format used to indicate a year classification. Assigning a classification means to assign a type and a weight.

    ______________________________________                                         line 1    10 DATE-OF-BIRTH                                                      line 2     15 YEAR-OF-BIRTH   PIC 99                                           line 3     15 MONTH-OF-BIRTH                                                                               PIC 99                                             line 4     15 DAY-OF-BIRTH    PIC 99                                          ______________________________________                                    

EXAMPLE C

The code fragment shown in Example C is an example of a declaration pattern which stores a year encapsulated within a date of the form YYMMDD (e.g. may hold a data value of 800102, meaning Jan. 2, XX80). The identification of such a pattern may be determined without the knowledge of actual customer data by simply examining the potential storage size and assignment of the labels.

In this instance, the labels have a recognizable structure, denoted by the COBOL level numbers 10, 15, 15, 15 in the second column. Since the label, DATE-OF-BIRTH on line 1, has a level number of 10 it may be used to refer to the set containing the three elements with smaller level numbers 15. Such a label is termed the parent of the labels numbered 15 as DATE-OF-BIRTH encapsulates the same memory location of the labels numbered 15, which are known as children. DATE-OF-BIRTH itself does not define storage but may be used as an alias to refer to the collection of YEAR-OF-BIRTH, MONTH-OF-BIRTH and DAY-OF-BIRTH.

For this example, assume that a "PIC 99" defines two bytes of storage. In a byte addressable storage scheme addresses would be shared as follows:

    ______________________________________                                         Start Address                                                                           End Address  Level   NumberLabel                                      ______________________________________                                         1000     1005         10      DATE-OF-BIRTH                                    1000                       15     YEAR-OF-BIRTH                                1002                       15     MONTH-OF-BIRTH                               1004                       15     DAY-OF-BIRTH                                 ______________________________________                                    

EXAMPLE D

There are other ways to share memory between labels in both declarative and procedure divisions which vary among computer languages. One skilled in the art can apply these techniques to a variety of situations where memory is shared.

In identifying that YEAR-OF-BIRTH is in fact a year, its parent is a pattern (i.e the label DATE-OF-BIRTH and, specifically, the string DATE) which confirms the suspicion that YEAR-OF-BIRTH might be a year. Moreover, month and day, as well as the three storage definitions (PIC 99) conform to a recognizable two byte (or two digit) year date pattern.

The above approach can be expanded to identify more complex patterns. Collections of collections may have names which may be used to determine the pattern of all variables in the collection. Limitation/constraints of the language can affect pattern matching classifications as well.

Initialization values for labels provide additional information as well. Assume that YEAR-OF-BIRTH, MONTH-OF-BIRTH, DAY-OF-BIRTH were initialized to 80, 01, 31, respectively, using a COBOL VALUE clause. 800131 can be interpreted as Jan. 31, 1980. In some cases, initialization values provide enough information to fully classify a label.

Declarative pattern matching techniques, while quite similar, vary by computer language and therefore are not restricted to the characteristics described herein.

Less information may be used to make a weaker conclusion (e.g. only analyzing line 2 above in Example D). Analyzing purely storage relationships (e.g. all but the adjacent labels in Example D) under certain conditions will provide clues to the information stored within. A skilled person in the art can create probable years (or any classification for that matter, such as date, month, day, and currency with any degree of certainty) by relying on a minimal set of characteristics.

Even non-declarative patterns can be identified by language specific operations or statistical information. For example, reserved words, such as labels used in system date calls, are easy to identify. Such labels are classified as pure years and are given the highest weight.

To manage the infinite number of characteristics, a pattern matching method incorporating the invention, employs one or more of the following:

boolean logic--for considering the many different characteristic which comprise a pattern;

precedence trees--some conclusions are partial and can be upgraded;

regular expressions--for consolidating permutations of labels, storage structures, etc.; and

subroutines--for abstracting sub-conclusions for more global conclusions.

A set of tools as these allows one to create, maintain and improve on a knowledge base of field classifications. The main use of the knowledge base, as described herein, is for scanning COBOL variables and will be hereater feferred to as "the scan knowledge base". An embodiment of a scan knowledge base which would match the above label in Example D can be represented by the following pseudo code:

Note: The regular expression "*YEAR*" will identify any label with the string YEAR in it such as YEAR-OF-BIRTH or LEAP-YEAR.

IF LABEL="*YEAR*" AND PARENT₋₋ LABEL="*DATE*" AND PIC="99" THEN CLASSIFY AS YEAR.

The form of the scan knowledge base may take on many different configurations as the knowledge base is improved. Tables, software, databases, artificial intelligence languages, statistical models may be combined to manage the learning system.

The scan process may take place before, during and/or after the process of reviewing all the operands in an application and may occur multiple times at some or all points in the date classification process. For the practical embodiment described herein, it is assumed that the scan process is applied only at the beginning of the entire process.

If a voting procedure is employed to enable the initial classification, the classification score for the variable shown above is 7 and its sub-fields would also have a score of 7. This is the maximum score a field can achieve, using such a scoring process. If a score exceeds 7, it is set to 7. For other formats, the score will be less than 7 which can be normalized to a value between 0.1 and 0.9 to provide a probability indicator that the operand comprises a probable year field.

As will be hereafter understood, a plurality of further tables are employed in the further analysis of the operands to enable a more precise classification to be assigned. A selection of the tables will be described hereinbelow. Table A is indicative of the fact that certain constants are associated with date calculations. Table A includes examples of most of these. The use of such a constant in certain kinds of calculations is an indicator that a variable is year-related.

                  TABLE A                                                          ______________________________________                                         Year Constants                                                                 Constant                                                                              Usage          Operators Involved                                       ______________________________________                                         1-11   Month of Fiscal Year                                                                          Comparison, Addition                                            End                                                                      4            Leap Year Test                                                                                    Division                                       7            Days in a week                                                                                    Comparison, Addition, Subtraction              8            Days in a week + 1                                                                       Comparison                                             12           Months in a year                                                                                 Comparison, Addition, Subtraction               13           Months in a year + 1                                                                    Comparison                                               28           Days in a Month (Feb.)                                                                     Comparison, Addition, Subtraction                     29           Days in a Month (Feb.)                                                                     Comparison, Addition, Subtraction                     30           Days in a Month                                                                                   Comparison, Addition, Subtraction              31           Days in a Month                                                                                   Comparison, Addition, Subtraction              100         Leap Year Test                                                                                      Division                                      365         Days in a Year                                                                                      Comparison, Addition, Subtraction             366         Days in a Year                                                                                      Comparison, Addition, Subtraction             367         Days in a Year + 1                                                                         Comparison                                             400         Leap Year Test                                                                                      Division                                      4000       Leap Year Test                                                                                       Division                                      ______________________________________                                    

As can be noted from an examination of Table A, if a numeral, for example "30", is associated with a comparison, addition or subtraction operator, an initial presumption can be made that the variable is year-related. As a further example, the value "400" is often used to test whether a year is a leap year (in a division action). Thus, the presence of one of the constants indicated in Table A provides one indicator that an associated operand field is year-related.

"Comparison" association operator Table B below is indicative of the situation when a pair of fields are associated with a comparison command. If Field 1 and Field 2 are initially classified as year fields, then a post-analysis classification, as judged by the association of the fields, will always indicate year fields for both Field 1 and Field 2. If, however, Field 1 is classified as a probable year field and Field 2 is classified as a year field, then the post analysis classification of Field 1 changes from probable year to year, as there few, if any, situations where any value other than another year is compared with a further year value.

                  TABLE B                                                          ______________________________________                                         Comparison Operator                                                            Initial Classification                                                                      Post Analysis Classification                                      Field.sub.-- 1                                                                        Field.sub.-- 2                                                                           Field.sub.-- 1                                                                               Field.sub.-- 2                                  ______________________________________                                         Year   Year      Year          Year                                            Year           Probable                                                                             Year                Year                                  Year           Not Year                                                                             Year                Year                                  Probable                                                                                  Year          Year            Year                                  Probable                                                                                  Probable                                                                                 F.sub.-- 1 = (F.sub.-- 1 + F.sub.-- 2)/2                                                 F.sub.-- 2 = (F.sub.-- 1 + F.sub.-- 2)/2        Probable                                                                                  Not Year                                                                                 Not Year        Not Year                                  Not Year                                                                                  Year          Year            Year                                  Not Year                                                                                  Probable                                                                                 Not Year        Not Year                                  Not Year                                                                                  Not Year                                                                                 Not Year        Not Year                                  ______________________________________                                    

In the classification noted in Table B, and other tables to follow, a Field 1 is denoted as (F₋₋ 1); Field 2 as (F₋₋ 2); and Field 3 as (F₋₋ 3). Note also from Table B that "not year" classifications can be changed to a "year" classification when a comparison operator requires such a field to be compared with a year field.

Association Tables C and D below are, respectively, used with addition operators and subtraction operators and logically relate initial classifications of associated operand fields to post analysis classifications of the same fields. It is important to understand that while fields 1 and 2 may be present in a first component program within the application, Field 3 is often present in another component program within the application. Any analysis of individual component program listings, without taking into account the interrelationships between the listings, overlooks valuable information which aids in achieving substantially higher accuracies of year field classification. The logical association of all of the inter-related fields that result from the utilization of operand table 26 operator table 28 and the various association tables (to be further described below) provides a high probability that all year-related fields are discovered and are properly classified. It is further to be noted that, in the main, the use of the association tables enables probable year field initial classifications to be changed to either a non-year classification or to a year classification and a non-year classification to be changed to either a probable year or a year classification.

The logic which enables the construction of the addition association table and subtraction association table shown below is readily apparent to those skilled in the art. Each line of each table is logically constructed in accordance with common usages in known programming environments.

                  TABLE C                                                          ______________________________________                                         Addition Operator                                                              Initial Classification                                                                          Post Analysis Classification                                                                         Field.sub.-- 3 if                       Field.sub.-- 1                                                                        Field.sub.-- 2                                                                               Field.sub.-- 3                                                                            Field.sub.-- 1                                                                       Field.sub.-- 2                                                                     Present                              ______________________________________                                         Year   Year     --       Year   Year   --                                      Year       Probable                                                                                  --                       --                              Year       Not Year                                                                                  --                       --                              Probable                                                                              Year           --             YearProbable                                                                         --                                  Probable                                                                              Probable       --             Probable                                                                          --                                     Probable                                                                              Not Year       --             Not Year                                                                             --                                  Not Year                                                                               Year             --                                                                                         YearYear                                                                                 --                              Not Year                                                                               Probable                                                                                    --              Probable                                                                            --                                   Not Year                                                                               Not Year                                                                                    --              Not Year                                                                             --                                  Year        Year                                                                                        Any                                                                                                  Year                            Year        Probable                                                                                Year                                                                                                 Yearar                              Year        Probable                                                                                Probable                                                                                Year                                                                                        Yearar                              Year        Probable                                                                                Not Year                                                                                Year                                                                                        Yearar                              Year        Not Year                                                                                Year                                                                                                 Yearar                              Year        Not Year                                                                                Probable                                                                                Year                                                                                        Yearar                              Year        Not Year                                                                                Not Year                                                                                Year                                                                                        Yearar                              Probable                                                                               Year             Year                                                                                       Yearr                                                                                    Year                            Probable                                                                               Year             Probable                                                                            Probable                                                                              Year                                                                                     Year                            Probable                                                                               Year             Not Year                                                                            Probable                                                                              Year                                                                                     Year                            Probable                                                                               Probable                                                                                   Year         F.sub.-- 2 ==                                                                        Year                                                             (F.sub.-- 1 +                                                                         (F.sub.-- 1 +                                                                                    F.sub.-- 2)/2                Probable                                                                               Probable                                                                                   Probable                                                                                 Probable                                                                          Probable                                                                                 Probable                            Probable                                                                               Probable                                                                                   Not Year                                                                                 Fd.sub.-- 1 =                                                                          F.sub.-- 2 =                                                                     Not Year                                                        F.sub.-- 1/2                                                                          F.sub.-- 2/2                                   Probalbe                                                                               Not Year                                                                                   Year                   Yearar                              Probable                                                                               Not Year                                                                                   Probable                                                                                 Probable                                                                              Not Year                                                                             Probable                            Probable                                                                               Not Year                                                                                   Not Year                                                                                  Not Year                                                                            Not Year                                                                              Not Year                            Not Year                                                                               Year            Year                                                                                       Yearear                                                                                   Year                            Not Year                                                                               Year            Probable                                                                              Not Year                                                                            Year                                                                                      Year                            Not Year                                                                               Year            Not Year                                                                              Not Year                                                                            Year                                                                                      Year                            Not Year                                                                               Probable                                                                                   Year             Yearar                                                                                  Year                             Not Year                                                                               Probable                                                                                   Probable                                                                                  Not Year                                                                             MAX                                                                                MAX                                                                           (F.sub.-- 2,-- 2,                                                      F.sub.-- 3)                                                                           F.sub.-- 3)                             Not Year                                                                               Probable                                                                                   Not Year                                                                                  Not Year                                                                             Not Year                                                                            Not Year                             Not Year                                                                               Not Year                                                                                   Year        Probableble                                                                              Year                                                                  YearYear                                                               F.sub.-- 1 = 0.5                                                                      F.sub.-- 2 = 0.5                               Not Year                                                                               Not Year                                                                                   Probable                                                                                  Not Year                                                                             Not Year                                                                            Not Year                             Not Year                                                                               Not Year                                                                                   Not Year                                                                                  Not Year                                                                             Not Year                                                                            Not Year                             ______________________________________                                    

                  TABLE D                                                          ______________________________________                                         Subtraction operator                                                           Initial Classification                                                                          Post Analysis Classification                                                                         Field.sub.-- 3 if                       Field.sub.-- 1                                                                        Field.sub.-- 2                                                                               Field.sub.-- 3                                                                            Field.sub.-- 1                                                                       Field.sub.-- 2                                                                     Present                              ______________________________________                                         Year   Year     --       Year   Year   --                                      Year       Probable                                                                                  --                       --                              Year       Not Year                                                                                  --                       --                                                              (Note 1)                                       Probable                                                                              Year           --             Year                                                                                 --                                  Probable                                                                              Probable       --             Probable                                                                          --                                     Probable                                                                              Not Year       --             Not Year                                                                             --                                  Not Year                                                                               Year             --                                                                                         YearYear                                                                                 --                              Not Year                                                                               Probable                                                                                    --              Probable                                                                            --                                   Not Year                                                                               Not Year                                                                                    --              Not Year                                                                             --                                  Year        Year                                                                                        Year                                                                                                 Error                           Year    Year         Probable                                                                                Year                                                                                             Not Year                       Year       Year      Not Year                                                                                Year                                                                                        Not Year                            Year        Probable                                                                                Year                                                                                    Year                                                                                        Yearar                              Year        Probable                                                                                Probable                                                                                    Year                                         Year        Probable                                                                                Not Year                                                                                Year                                                                                        Not Year                            Year        Not Year                                                                                Year                                                                                    Year                                                                                        Yearar                              Year   Not Year Probable Year   Not Year                                                                              Year                                    Year   Not Year Not Year Year   Not Year                                                                              Year                                    Probable                                                                              Year     Year     Not Year                                                                              Year   Year                                    Probable                                                                              Year     Probable Probable                                                                              Year   Probable                                Probable                                                                              Year     Not Year Year   Year   Year                                    Probable                                                                              Probable Year     Probable                                                                              Probable                                                                              Year                                    Probable                                                                              Probable Probable Probable                                                                              Probable                                                                              Probable                                Probable                                                                              Probable Not Year Fd.sub.-- 1 =                                                                         F.sub.-- 2 =                                                                          Not Year                                                         F.sub.-- 1/2                                                                          F.sub.-- 2/2                                   Probable                                                                              Not Year Year     Year   Not Year                                                                              Year                                    Probable                                                                               Not Year                                                                                   Probable                                                                                 Probable                                                                              Not Year                                                                             Probable                            Probable                                                                               Not Year                                                                                   Not Year                                                                                  Not Year                                                                            Not Year                                                                              Not Year                            Not Year                                                                               Year            Year                                                                                       Yearear                                                                                   Year                            Not Year                                                                               Year            Probable                                                                              Not Year                                                                            Year                                                                                      Year                            Not Year                                                                               Year            Not Year                                                                              Not Year                                                                            Year                                                                                      Year                            Not Year                                                                               Probable                                                                                   Year             Yearar                                                                                  Year                             Not Year                                                                               Probable                                                                                   Probable                                                                                  Not Year                                                                             MAX                                                                                MAX                                                                           (F.sub.-- 2,-- 2,                                                      F.sub.-- 3)                                                                           F.sub.-- 3)                             Not Year                                                                               Probable                                                                                   Not Year                                                                                  Not Year                                                                             Not Year                                                                            Not Year                             Not Year                                                                              Not Year Year     Not Year                                                                              Year   Year                                    Not Year                                                                               Not Year                                                                                   Probable                                                                                  Not Year                                                                             Not Year                                                                            Not Year                             Not Year                                                                               Not Year                                                                                   Not Year                                                                                  Not Year                                                                             Not Year                                                                            Not Year                             ______________________________________                                          Note 1:This indicates the year in 9's complement form.                   

As shown below, a division operator association Table E is utilized. It is generally used only for fields classified as year fields and Field 3 is the numerical remainder of the operation. The test for Field 3 is an IF statement that is executed subsequent to the divide operation.

                  TABLE E                                                          ______________________________________                                         Division Operator                                                                                      Post Analysis                                          Initial Classification  Classification                                         Field.sub.-- 1                                                                           Field.sub.-- 2                                                                             Field.sub.-- 3                                                                           Field.sub.-- 2                                 ______________________________________                                         Constant of 4                                                                            Year        Tested for 0                                                                             Year                                           100, 400 or 4000                                                               Constant of 4,                                                                               Probable Year                                                                              Tested for 0                                                                              Year                                      100, 400 or 4000                                                               Constant of 4,                                                                              Non-year           Tested for 0                                                                       = MAX(.5, 1-((1-                           100, 400 or 4000                                                                                                         F.sub.13 2)/2))                      ______________________________________                                    

To illustrate the use of Table E, the following code listing for a leap year determination is provided. The leap year test is determined in Field 3.

    ______________________________________                                         SET Leap-Year EQUAL TO FALSE                                                   DIVIDE 4 INTO Year GIVING Temp REMAINDER Leap-Year-                            Test                                                                           IF Leap-Year-Test EQUAL 0 THEN                                                 SET Leap-Year TO TRUE                                                          DIVIDE 100 INTO Year GIVING Temp REMAINDER                                     Leap-Year-Test                                                                 IF Leap-Year-Test EQUAL 0 THEN                                                 SET Leap-Year TO FALSE                                                         DIVIDE 400 INTO Year GIVING Temp REMAINDER                                     Leap-Year-Test                                                                 IF Leap-Year-Test EQUAL 0 THEN                                                 SET Leap-Year TO TRUE                                                          DIVTDE 4000 INTO Year GIVING Temp                                              REMAINDER Leap-Year-Test                                                       IF Leap-Year-Test EQUAL 0 THEN                                                         SET Leap-Year TO FALSE                                                  END IF                                                                         END IF                                                                         END IF                                                                        END IF                                                                         ______________________________________                                    

Association Table F is used when a move operator is present.

                  TABLE F                                                          ______________________________________                                         Move Operator                                                                  Initial Classification                                                                        Post Analysis CIassification                                    Field.sub.-- 1                                                                          Field.sub.-- 2                                                                           Field.sub.-- 1                                                                              Field.sub.-- 2                                 ______________________________________                                         Year     Year      Year         Year                                           Year             Probable                                                                               Year               Year                               Year             Not Year                                                                               Year               Year                               Probable     Year            Year                                                                                          Year                               Probable     Probable                                                                                   MAX(F.sub.-- 1,F.sub.-- 2)                                                                MAX(F.sub.-- 1,F.sub.-- 2)                 Probable     Not Year                                                                                   Not Year                                                                                      Not Year                               Not Year     Year            Not Year                                                                                  Year                                   Not Year     Probable                                                                                   Not Year                                                                                      Not Year                               Not Year     Not Year                                                                                   Not Year                                                                                      Not Year                               ______________________________________                                    

Turning now to FIGS. 4a-4c, the detailed operation of the method of the invention will be described. Initially, as shown in FIG. 4a, memory space is allocated for operand table 26 and operator table 28 in program memory 14 (box 100). Thereafter, the data definition segment of application 16 (and any programs associated therewith) is scanned and each operand listed therein is identified, and its format is determined. From the label and its format, an initial classification is assigned, i.e., as to whether it initially appears to be a year field, a probable year field, or a non-year field (box 102). The flags in reclassification column 35 are reset. As described above, the initial classifications are accomplished through use of known methods of analysis. The results of the scan of the data definition segment are inserted into operand table 26 (box 104).

Thereafter, the procedure portion of application 16 and its associated programs is parsed; and every field with an operator is identified, as is the operator (box 106). Next (box 108), operator table 28 is built by listing every operator found in the procedure portion of the application, along with the operands identified therewith. The initial classifications of each operand from operand table 26 are also inserted into operator table 28.

At this stage, operand table 26 and operator table 28 are complete, with operand table 26 including a listing of each operand and an initial field classification thereof, and operator table 28 including a listing of every operator in application 16 and its associated operands, along with initial classification indications thereof.

Turning to FIG. 4b, the procedure now turns to a refinement of the initial classification of each of the operands to arrive at a more accurate classification thereof. The procedure commences by examining all operators of a first type, e.g., move operators, and the associated operands found in operator table 28. In the first portion of the procedure, operator entries whose Field 1 initial classification indicate a year classification, are processed. Once all such operator entries of the first type have been examined, all entries of a next operator type with a Field 1 year classification are searched, etc. until all operator types and their associated operands have been analyzed. Thereafter, the procedure is repeated for operators having a Field 1 initial classification of probable year.

In further detail, operator table 28 is initially searched for a first entry therein of the chosen operator type with a Field 1 classification of "year" (box 110). Then (box 112), the operand association table for the operator is accessed and its "initial" classification column is searched to determine an entry therein with identical operand classifications as those operands associated with the chosen initial operator entry from operator table 28. When such an entry is found, the post analysis classification portion thereof is examined and if a field re-classification is indicated (i.e., by an entry for an operand in a post-analysis classification column that is different from the initial classification portion), the indicated operand reclassification is entered in both operator table 28 and operand table 26 (box 116), the associated reclassification flag set, and the procedure moves to box 118.

There, steps 110, 112, 114 and 116 are repeated for each first operator type entry in operator table 28 having a Field 1=year. After no further operator entries of the first type remain to be analyzed and only if no operand reclassifications are indicated as having been performed on the last iteration, does the procedure moves to box 124. Otherwise (box 122), steps 110, 112, 114, 116 and 118 are repeated for each first operator type entry in operator table 28 having Field 1=year. This repetition occurs because any reclassification of an operand can affect other related operands and may cause further reclassification actions on a succeeding iteration.

Note from the above that each classification of an operand is dependent upon both the operator with which it is associated and other operands present in the same operator entry. Those operands may be reside in the same program or may be from another program in the application. As a result of the steps shown in FIGS. 4a and 4b, there is a high probability that errors in the initial classification of operands associated with first operator entries will be corrected and that proper classifications will be reconfirmed.

Turning to FIG. 4c, steps 110-122 are now repeated for the next operator type with a Field 1=year, using an association table for the next operator type (box 124). Thereafter, when all operator types having a Field 1=year operand have been analyzed (box 126), the procedure repeats for all operator entries in operator table 28 having a Field 1 operand=probable year (box 128). This procedure will not discover more year classifications but will change the probabilities assigned to certain probable year entries to enable a more accurate decision to be made with respect to which entries require further analysis. In this regard, any probable year entry with a probability level below a set threshold value is listed in a "programmer attention" table for further analysis by the user.

Special situations may arise during this procedure which require further analysis in order to resolve a complex classification, such as resolvable or unresolvable modals. For the practical embodiment described herein, detection of a complex classification will occur for the association defined in the subtraction operator association in Table D when field₋₋ 1, field₋₋ 2 and field₋₋ 3 are all assigned a year classification. Once detected, it is assumed that at least one of the three fields is both a year and not year classification and therefore should be assigned a modal classification. A modal classification, by definition, means that classifications vary by operand instance for the given operand.

To analyze modal variables (see FIG. 4d), a more conservative approach should be applied for the modal operand and to all operands which interact with the modal operand in the application (box 130). Operands which interact with the modal operand are affected by the modal operand. Since these operands are analyzed by operand instance, they are given a special name, i.e., affected operands. Such a conservative approach does not assume that all operand instances of an operand are assigned a single classification when reclassifying operands. Instead, each operand instance for modals and affected operands is treated as a separate operand and therefore derives its classification independently. This process is repeated until no further information can be learned for all modal and affected operands (box 132).

For each affected operand, all of the operand instances are examined, as a whole, for consistency to determine if more analysis is required (box 134). The operator association tables are applied as if one operand instance was associated to another operand instance with a move operator (Table F). Care is taken to insure that classifying operand instances is performed correctly. First simple code logic scenarios are examined, such as linear blocks of non-branching code where an operand is set once and then read many times. Next, slightly more complex, non-branching code with multiple sets for the same variable are examined. Variables classified at this point are assigned a slightly lower probability, if applicable, since each classification is less certain as code flow becomes more complex.

The process continues for each type of code logic, starting from simple to complex (box 136) until no classifications are revised. Some associations are not made across instances where the certainty is low or zero due to non-deterministic or highly complex code flow scenarios.

The above-noted procedure enables identification of year fields with high probability, and thereafter enables each of those year fields to be automatically accessed and to have their year designation altered in such a manner as to enable a removal of the ambiguity which arises from the onset of the year 2000 and forward. A preferred method for revising the year format and for enabling the year conversion procedure is described in U.S. patent application Ser. No. 08/657,657, entitled "Date Format and Date Conversion Procedure" to Brady. The disclosure of the aforementioned patent application is incorporated herein by reference.

Hereafter is a pseudo-code listing which carries out the procedure shown in the flow diagrams of FIGS. 4a-4d.

    ______________________________________                                         Loop Once On Each Operator (Move, Comparison,                                  Subtraction, Addition, Division)                                               Set Current First.sub.-- Table_Entry to the first                              First_Table.sub.-- Entry marked as Year                                        Loop Until Year.sub.-- State.sub.-- Change = False                             Set Year.sub.-- State.sub.-- Change to False                                   Loop Until All Second.sub.-- Table.sub.-- Entries using the                    Current.sub.-- First.sub.-- Table Entries's field label or                     aliases are processed                                                          Set Current.sub.-- Second.sub.-- Table.sub.-- Entry to the next                (first) Second table.sub.-- Entry using the                                    Current.sub.-- First.sub.-- Table.sub.-- Entry's label or alias                If Current.sub.-- Second.sub.-- Table.sub.-- Entry.sub.-- Operator =           Current.sub.-- Operator                                                                Then Process according to the                                                  corresponding operator table and if                                            there is a change in a year's status,                                          mark it as changed and                                                         Set Year.sub.-- State.sub.-- Change = True                              End if                                                                         End Loop                                                                       End Loop                                                                      Comment: The following loop will not discover more                             years but will change the probability assigned to a                            probable year.                                                                 Set Current.sub.-- First.sub.-- Table.sub.-- Entry to the first                First.sub.-- Table.sub.-- Entry marked as Probable year                        Loop Until Year.sub.-- State.sub.-- Change = False                             Set Year.sub.-- State.sub.-- Change to False                                   Loop Until A11 Second.sub.-- Table.sub.-- Entries using the                    Current.sub.-- First.sub.-- Table.sub.-- Entry's field label or                a1iases are processed                                                          Set Current.sub.-- Second.sub.-- Table.sub.-- Entry to the next                (first) Second.sub.-- Table.sub.-- Entry using the                             Current.sub.-- First.sub.-- Table.sub.-- Entry's label or alias                If Current.sub.-- Second.sub.-- Table.sub.-- Entry.sub.-- Operator =           Current.sub.-- Operator                                                                Then Process according to the                                                  corresponding operatar table and if                                            there is a change in a year's                                                  probability mark it as changed and                                             Set Year.sub.-- State.sub.-- Change = True                             End if                                                                         End Loop                                                                       End Loop                                                                       End Loop Once                                                                  ______________________________________                                    

It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims. 

We claim:
 1. A method for operating a computer to examine a software application including operands and operators, and to identify operand fields therein which include a year value, the computer including a scan knowledge base with scan rules that enable characteristics of operands to be identified and classified, said method including the steps of:a) establishing operand association table means comprising an operand association table for each operator type, for logically determining, based upon interrelationships of operands associated with an operator, whether an operand having a classification as a year field, a probable year field or a not-year field should be assigned a revised classification; b) reviewing said application, using the scan knowledge base and scan rules to identify and classify each operand which can be classified as a year field, a probable year field or a not-year field, and listing each operand classified as a year field, a probable year field or a not-year field in an operand table; c) reviewing said application to identify every operator listed therein and listing as an entry in an operator table, said every operator and any associated operands; d) for each respective operand listed in said operand table, finding in said operator table each operator entry with which said respective operand is associated; and e) for each operator entry identified in step d), determining from: operand(s) associated therewith, said each respective operand, and said operand association table for the operator type of said each operator entry, whether said classification for said each respective operand in said operand table should be altered; and wherein steps d) and e) are first performed for all operators of a first operator type and are then repeated, in succession, for all operators of second and additional types.
 2. The method as recited in claim 1, wherein said scan knowledge base includes information which enables identification of data structure arrangements.
 3. The method as recited in claim 1, wherein said scan knowledge base includes initialization values for operands which enable identification of year fields, probable year fields and not-year fields.
 4. The method as recited in claim 1, wherein steps d), e) are first performed for all operands classified as year fields and are then repeated for all operands classified as probable year fields.
 5. The method as recited in claim 1, wherein if any operand classification has been modified during steps d) and e), steps d) and e) are repeated, using current classifications for each respective operand entry in said operand table.
 6. The method as recited in claim 1, wherein if any modal operand is detected, a modal operand being an operand that may have at least two different classifications in a code listing, and if any affected operand instance has been modified during steps d) and e), steps d) and e) are repeated, using current classifications for each respective operand entry in said operand table and each modified operand instance in said operator table.
 7. The method as recited in claim 6, wherein if an operand instance has been modified based on examination of code logic scenarios, then steps d) and e) are repeated, using current classifications for each respective operand entry in said operand table and each modified operand instance in said operator table.
 8. The method as recited in claim 1, wherein step b) examines data stored in adjacent memory addresses as an aid in said determining a classification of an operand stored in at least one of said adjacent memory addresses.
 9. A memory means for use in conjunction with a computer, said memory means enabling said computer to examine a software application including operands and operators, to identify operand fields therein which include a year value, said computer including (i) operand association table means comprising an operand association table for each operator type, for providing, based upon interrelationships of operands associated with an operator, indications of whether an operand having a classifications as a year field or a probable year field should be assigned a revised classification and what said revised classification should be, and (ii) a scan knowledge base with scan rules that enable characteristics of operands to be identified and classified, said memory means comprising:a) first means for controlling said computer to review said application, in conjunction with said scan knowledge base, to identify each operand in said application which can be classified as a year field, a probable year field or a not-year field and to list at least each operand thereby classified as a year field, a probable year field or a not-year field in an operand table; b) second means for controlling said computer to review said application to identify every operator listed therein and for listing as an entry in an operator table, said every operator and any associated operands; c) third means for controlling said computer to locate in said operator table, for each respective operand listed in said operand table, each operator entry with which said respective operand is associated; and d) fourth means for controlling said computer to determine, for each operator entry located in said operator table, from: (i) operand(s) associated therewith, (ii) said each respective operand, and (iii) said operand association table for the operator type of said each operator entry, whether said classification for said each respective operand in said operand table should be altered; and wherein said third means and fourth means operate upon all operands classified as year fields and then repeat for all operands classified as probable year fields.
 10. The memory means as recited in claim 9, wherein said scan knowledge base includes information rules which enables identification of data structure arrangements.
 11. The memory means as recited in claim 9, wherein said scan knowledge base includes initialization values for operands which enables identification of year fields and probable year fields.
 12. The memory means as recited in claim 9, wherein said third means and fourth means operate upon all operands classified as year fields and then repeat for all operands classified as probable year fields.
 13. The memory means as recited in claim 9, wherein if any operand classification has been modified by said fourth means, said third means and fourth means repeat their operations, using current classifications for each respective operand entry in said operand table.
 14. The memory means as recited in claim 9, wherein if any modal operand is detected by said first means, wherein a modal operand being an operand that may have at least two different classifications in a code listing, and if any affected operand instance has been modified as a result of such a determination by means d), means c) and d) are caused to repeat their operations, using current classifications for each respective operand entry in said operand table and each modified operand instance in said operator table.
 15. The memory means as recited in claim 9, wherein if an operand instance has been modified based on examination of code logic scenarios, then means c) and d) are caused to repeat their operations, using current classifications for each respective operand entry in said operand table and each modified operand instance in said operator table.
 16. The memory means as recited in claim 9, wherein means a) examines data stored in adjacent memory addresses as an aid in said determining a classification of an operand stored in at least one of said adjacent memory addresses. 